Telephone-transmitter.



, w No. 732,285. PATENTED JUNEBO, 1903.,

E. B. PAHNESTOGK.

TELEPHONE TRANSMITTER.

APPLICATION FILED D20. 5, 1901.

H0 MODEL.

Patented Tune 80, 1908,

PATENT OFFICE.

ERNEST B. FAI-INESTOCK, OF NEW YORK, N. Y.

TELEPHONE-TRANSMITTER.

SPECIFICATION formingpart of Letters Patent No. 732,285, dated June 30, 1903.

Application filed December 5. 1901. Serial No. 84,756. (No model.)

To all whom it may concern.-

Be it known that I, ERNEST B. FAHNESTOOK, a citizen of the United States, residing at New York city, county and State of New York, have invented certain new and useful Improvements in Telephone-Transmitters, of which the following is a specification.

My invention relates in general to electric telephones, and more especially to those'employingmicrophone-transmitters; and it consists of an improved mounting for such microphones in the sound-receiving chamber.

. In the class of microphone-transmitters employing granular conducting material, such as finely-divided carbon, upon which an electrode in the shape of a disk operates under the sound-vibrations to vary the conductivity thereof, it has heretofore been generally customary to arrange said microphones in such position that the faces of the disk or disks are substantially vertical. As a result the granular material has a tendency to pack down into the lower portion of the microphone-chamber, and thereby diminish its sensitiveness to the vibrations of the electrodes and also to unequally distribute the granular material with reference to the surface of said electrodes. I havebvercome this disadvantage by so placing the microphone that the faces of the electrodes are arranged at an oblique angle to the plane of the horizon, whereby the tendency of the granular material to sag down into the lower portion of the microphone-chamber is largely obviated and its even contact with the electrode-faces secured. I also prefer to mount the microphone in a substantially squarecasing, so that it may be from time to time withdrawn and reinserted in different positions within the rectangular receivingchamber, thereby reversing or varying the action of gravitation upon the granular particles.

An apparatus embodying my invention in its preferred form is illustrated in the accompanying sheet of drawings, in which Figure 1 is a side elevation of a telephonetransmitter constructed in accordance with my invention. Fig. 2 is a cross-section of the same taken on line 2 2 of Fig. Fig. 3 is a side elevation, partly in section, of the structure shown in Fig. 1, the section at the left-hand side being taken upon a vertical used in my invention.

vmouthpiece 3 connected thereto.

plane and the section at the right-hand side being taken on the line 3 3 of Fig. 2. Fig. 4 is aside view of the microphone preferably Fig. 5 is an edge view of the same. Fig. 6 is a detail view of the parts of the microphone, the same being separated, but arranged in their proper relative positions.

Throughout the drawings like referencefigures indicate like parts.

The casing 1 for the microphone is preferably cast integrally withthe supportingarm 2 and has any convenient form of flaring The supporting-arm is hinged by the pivot 4 to the supporting-bracket 5, which latter contains usually an induction-coil 6. The innerend of the supporting -bracket arm may have a screw-threaded recess 7, into which a bindingscrew for one of the wire connections may be introduced.

The sound-receiving chamber 8, formed in the casing 1, is preferably rectangular in cross-section, as shown in Fig. 2, and contains a microphone 9, which is inclosed in a rectangular casing adapted to fit, into this chamber, as shown in Figs. 2 and 3. Preferably this microphone casing is approximately square in shape, as shown, so that it may be reversed or altered in its position by withdrawing it from and reinserting it in the sound-receiving chamber.

The preferred form of microphone is shown in detail in Fig. 6 and contains an interior ring 10, against which small diaphragms 11 11 are held by an inclosing two-part casing 12 12, each of the parts 12 12 being provided with an annular shoulder 18,which surrounds the diaphragms and interior ring. The electrodes 14 14, preferably formed of carbon, are supported on metal disks 13 13 which latter are provided with screw-threaded bosses 15 15, adapted to pass through openings in the center of the diaphragms, as shown. WVashers or exterior plates 16 16 fit over these bosses and when forceddown by the screwthreaded nuts 17 17 clamp the diaphragms firmly between said electrode-disks 13 13 and said washers 16 and 16. The parts are all held together by any convenient means holding the two-part casing 12 12 together. I have shown screws 19 19 in Figs. 4 and 5.

Too

One of the wires of the external electric circuit is shown at 20 in Fig. 1, and this is connected to a binding-post 21 in the casing l,from which binding-post the wire 22 extends to one of the electrodes of the microphone. The other electrode of said microphone may be connected to the arm 2 in any convenient way, as by a wire 23,- which is soldered onto the exterior casing 12, as indicated in Fig. 4.

lVithin the chamber formed between the diaphragms 11 and 11 and the internal ring 10 and between the electrodes of the microphone is a mass of granular material, usually finely divided carbon, as shown at 24 in Fig. 2.

The microphone fits quite closely into the chamber 8 and may be retained there in any convenient manner, as by means of a setscrew 25. (Shown in Fig. 2 of the drawings.)

The method of operation of my invention is as follows: The sound-receiving chamber 8, of rectangular cross-section, is so formed that its sides are inclined at an oblique angle to the plane of the horizon. IVhen the microphone 9 is introduced, the faces of the disk electrodes of the diaphragms are also inclined at the same angle to the horizon. The granular material held between the electrodes is consequently in a large measure supported by the under electrode and friction tends to prevent the packing down of such carboninto the lower portion of the microphoneehamber. Thus contact is maintained and more evenly distributed over the face of the electrode and the carbon is pressed against all portions thereof with approximately the same degree of force. As there is of course, however, a slight remaining tendency for the carbon to slide down the face of the electrode the partial occurrence of such shifting of the material may be rectified by withdrawing the microphone from time to time and reversing it before reinserting it in the transmitter. By making the microphone approximately square in its outline, as'shown in Fig. 4, itis possible to obtain four positions of adjustment, and thereby maintain the even distri bution of the carbon by occasional shifting of the microphone into these four different positions about an axis perpendicular to the faces of the disk electrodes.

The advantages of my invention comprise the neat and compact construction resulting from the above-described proportion of the parts, the prevention or diminishing of the tendency of the loose carbon to pack down in the bottom of the micropholie-chamber, and the improved quality of speech-transmission resulting therefrom.

It is evident, of course, that various changes could be made in the details of the apparatus described and shown without departing from the principle of my invention so long as its essential features are retained.

While I have shown a double-faced microphone, the feature of inclining the face of the electrode to the electrode might be applied to equal advantage in other forms of microphone. VVhile I have shown a rectangular sound-receiving chamber, the inclined microphone might be located in sound-receiving chambers of other forms. Other forms of microphone might be substituted for the specific construction shown, &c., but all such modifications of construction I should still consider within the scope of my invention.

Having therefore described my invention, what I claim as new, and desire to protect by Letters Patent, is

1. In a telephone-transmitte1',the combination with a support provided with a soundchamber whose sides are at an angle to the plane of the horizon, a microphone comprising a chamber whose sides are also at an angle to the plane of the horizon, a pair of electrodes mounted in said chamber, a body of granular material located in said chamber, and sound-diaphraglns carried by the microphone.

2. In a telephone-transinitter, the combination with a support having a sound-chamber, of rectangular cross-section with its sides inclined at an angle to the plane of the horizon, and a removable microphone contained in a rectangular casing adapted to fit into said chamber so that the faces of the microphone will be similarly inclined and irrespective of which end of the microphone is placed uppermost.

In testimony whereof I affix my signature in the presence of two witnesses.

ERNEST B. FAI-INESTOCK. 

